Electric motors commonly produce a rotational output, but many mechanisms require that a linear movement be driven by the motor. A leadscrew assembly is one approach for translating the rotational movement of the motor to the required linear movement. In the conventional leadscrew assembly, the thread of an externally threaded leadscrew engages a recirculating ball nut structure, which in turn is engaged to the structure to be driven linearly. As the leadscrew turns, the ball nut structure and the driven structure move linearly.
This conventional leadscrew assembly is relatively expensive to produce due to the precision machining required. It is also limited to relatively large-size devices and coarse thread pitches because of the size of the balls used in the recirculating ball nut structure. The conventional leadscrew assembly may be subject to excessive wear of the threads, particularly if there is any misalignment in the assembly. The conventional leadscrew assembly also requires careful alignment between the motor, the leadscrew, and the driven structure because of the mechanical engagements at each end of the leadscrew.
An advance in overcoming some of these disadvantages is described in U.S. Pat. No. 5,636,549, whose disclosure is incorporated by reference. The '549 patent discloses a leadscrew in which the thread structure is defined by a wire wound helically around a cylindrical shaft. A leadscrew-nut assembly is also disclosed for engaging the leadscrew to the linear slide assembly.
The approach of the '549 patent is operable for many applications but is not optimal for other applications such as those requiring medium-duty operation where there is a concern with possible misalignment. There is a need for realizing the advantages of the basic approach disclosed in the '549 patent, but in a form more suitable to these other applications, and which reduces the concern with alignment of the elements. The present invention fulfills this need, and further provides related advantages.